Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-11-01
2004-11-02
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S212000, C524S430000, C524S439000
Reexamination Certificate
active
06812268
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to novel systems and methods for polymerizing nanoparticles within a polymer matrix and to novel methods for fabricating materials containing nanoparticles in a polymer matrix.
2. Description of the Related Art
Polymers are substances made of “many parts”. In most cases the parts are small molecules which react with each other to form a larger molecule having hundreds, thousands, or millions of the small molecules linked together. A molecule used in producing a polymer is a monomer. A polymer made entirely from molecules of one monomer is referred to as a homopolymer. Chains that contain two or more different repeating monomers are copolymers.
The resulting molecules may be long, straight chains, or they may be branched, with small chains extending out from the molecular backbone. The branches also may grow until they join with other branches to form a huge, three-dimensional matrix. Variants of these molecular shapes are among the most important factors in determining the properties of the polymers created.
The size of polymer molecules is important. This is usually expressed in terms of molecular weight. Since a polymeric material contains many chains with the same repeating units, but with different chain lengths, average molecular weight must be used. In general, higher molecular weights lead to higher strength. But as polymer chains get bigger, their solutions, or melts, become more viscous and difficult to process.
Life as we know it could not exist without polymers. Proteins, with large numbers of amino acids joined by amide linkages, perform a wide variety of vital roles in plants and animals. Carbohydrates, with chains made up of repeating units derived from simple sugars, are among the most plentiful compounds in plants and animals. Both of these natural polymers are important fibers. Proteins are the basis for wool, silk and other animal-derived filaments. Cellulose as a carbohydrate occurs as cotton, linen and other vegetable fibers. The naturally occurring form of the base polymers limits the properties of these fibers. Some, like linen and silk, are difficult to isolate from their sources, which makes them scarce and expensive. There are, of course, many other sources of proteins and cellulose. Wood pulp is an example of a cellulose source. Natural polymers, however, tend to be very difficult to work with and form into fibers or other useful structures. The inter-chain forces can be strong because of the large number of polar groups in the molecular chains. Thus, natural polymers usually have melting points that are so high that they degrade before they liquefy.
The most useful molecules for fibers are long chains with few branches and a very regular, extended structure. Thus, cellulose is a good fiber-former. It has few side chains or linkages between the sugar units forcing its chains into extended configurations. However, starches, which contain the same basic sugar units, do not form useful fibers because their chains are branched and coiled into almost spherical configurations. Synthetic polymers offer more possibilities, since they can be designed with molecular structures that impart properties for desired end uses. Many of these polymers are capable of dissolving or melting, allowing them to be extruded into the long, thin filaments needed to make most textile products.
Synthetic polymer fibers can be made with regular structures that allow the chains to pack together tightly, a characteristic that gives filaments good strength. Thus, filaments can be made from some synthetic polymers that are much lighter and stronger than steel. Bullet-proof vests are made from synthetic fibers.
There are two basic chemical processes for the creation of synthetic polymers from small molecules: (1) condensation, or step-growth polymerization and (2) addition, or chain-growth polymerization.
In step-growth polymerization, monomers with two reactive ends join to form dimers (two parts joined together), then “trimers” (three parts), and so on. However, since each of the newly formed oligomers (short chains containing only a few parts) also has two reactive ends, they can join together; so a dimer and a trimer would form a pentamer (five repeating parts). In this way the chains may quickly great length achieve large size. This form of step-growth polymerization is used for the manufacture of two of the most important classes of polymers used for textile fibers, polyamide (commonly known as nylon), and polyester.
There are many different commercial versions of polyester in a wide variety of applications, including plastics, coatings, films, paints, and countless other products. The polymer usually used for textile fibers is poly(ethylene terephthalate), or PET, which is formed by reacting ethylene glycol with either terephthalic acid or dimethyl terephthalate. Antimony oxide is usually added as a catalyst, and high vacuum is used to remove the water or methanol byproducts. High temperature (>250° C.) is necessary to provide the energy for the reaction, and to keep the resultant polymer in a molten state.
PET molecules are regular and straight, so their inter-chain forces are strong—but not strong enough to prevent melting. PET chains are long and “rigid” and their inter-chain forces, while somewhat strong, do not allow for significant alignment of groups on the chain that would interact strongly with other chains. In contrast, with cellulose the inter-chain forces are almost as strong as the hydrogen bonding that occurs in water. Thus, PET is a “thermoplastic” material; that is, it can be melted and then solidified to form specific products. Since its melting point is high, it does not soften or melt at temperatures normally encountered in laundering or drying. Another important property of PET is its Tg, or “glass transition temperature”. When a polymer is above its glass transition temperature, it is easy to change its shape. Below its Tg, the material is dimensionally stable and it resists changes in shape. This property is very important for textile applications because it allows some fibers, and the fabrics made from them, to be texturized or heat-set into a given shape. This can provide bulk to the yam, or wrinkle resistance to the fabric. These set-in shapes remain permanent as long as the polymer is not heated above its Tg. Because its chains are closely packed and its ester groups do not form good hydrogen bonds, polyesters are also hydrophobic (i.e., they do not absorb water). This property also requires special dyeing techniques.
There are also many important classes of synthetic polyamides (nylons) and they have a wide variety of commercial uses. These are usually distinguished from each other by names based on the number of carbon atoms contained in their monomer units. As with polyesters, polyamides are formed by step-growth polymerization of monomers possessing two reactive groups. Here, the reactive functions are acids and amines. The monomers used may have their two reactive functions of the same chemical type (both acids, or both amines), or of different types. Thus, nylon 6,6—a very common fiber polymer—is made by reacting molecules of adipic acid (containing six carbons in a chain, with an acid function at each end) with hexamethylene diamine (also six carbon atoms, with amine functions at each end). In another variant the diamine contains ten carbons atoms, the product designated nylon 6,10.
The other common polyamide fiber polymer is nylon 6. Its monomer has six carbons in the chain, with an amine at one end and an acid at the other. Thus only one form of monomer is needed to carry out the reaction. Commercial production of nylon 6 makes use of caprolactam, a derivative that provides the same result.
As with the polyesters, nylons have regular structures that permit good inter-chain forces, imparting high strength. Both nylon 6 and nylon 6,6 have melting points similar to PET, but have a lower Tg. Also, since the amide functions in nylon chains are good at h
Schneider Thomas W.
White Robert C.
Kilpatrick & Stockton LLP
Science Applications International Corporation
Yoon Tae H.
LandOfFree
Methods for material fabrication utilizing the... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Methods for material fabrication utilizing the..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Methods for material fabrication utilizing the... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3355664